Process for producing a reinforcing rod for concrete



Feb. 10, 970 s. REHM ETAL r 3, 4,

' I PROCESS FOR PRODUCiNG A REINFORCING ROD .FOR CONCRETE Filed Jan. s, 1968 v i 4 Sheets-Sheet s F 19.70 V G. REHM ETAL 3,49

' Feb. 10, 1970 5, REHM ETAL 3,494,164

PROCESS FOR PRODUCING A REINFORCING on FOR CONCRETE Filed Jam 5, 1968 4 Sheets-Sheet 1 a. REHM ETAL Feb. 10, 1970 P R ocEss FOR rnonucin a A REINFORCING ROD FOR CONCRETE 4 Sheets-She et 4 Filed Jan. 5, 1968 b d J m f ml U.S. Cl. 72-187 11 Claims ABSTRACT OF THE DISCLOSURE A process for producing a reinforcing rod for concrete in which a plurality of axially extending flat portions are formed on the circumference of a cylindrical rod at equal angular intervals, after which the rod is cold worked in the regions between the fiat portions to form a plurality of spaced ribs having lateral flanks smoothly blending with the surface of the rod between the ribs and ends which smoothly blend into the fiat portions.

BRIEF SUMMARY OF THE INVENTION This invention relates to processes for producing reinforcement rods for use in concrete structures.

It is known to reinforce concrete with steel rods having ribs on their circumference. Such ribs are provided for better anchoring of the rod in the concrete. For the purpose of good anchoring it is desirable that these ribs be fairly high. Reinforcing rods for concrete are known, whose ribs are at right angles to the axis of the rod or are inclined to the 'axis. Reinforcing rods are normally produced by hot rollingsteel to the shape of round rods. The ribs can be produced in the hotrolling process. However, it is also possible to produce a smooth rod by hot rolling and to form the ribs on its surface by subsequent cold-rol1ing. Such a follow-up cold-rolling operation increases the tensile strength of the rod. However, it simultaneously decreases its impact strength. This decrease can become so significant that cracks will form in the rod when it is bent. This occurs in particular if there is no continuous and gradual transition from the rib to the smooth unribbed portion of the rod surface.

There is another known process in which a smooth rod is first produced by hot rolling and the strength of the rod is thereafter increased over'its entire cross-section by a cold forming operation, for example, by cold drawing through a round nozzle. The ribs are thereafter formed on the surface of the rod by cold rolling the rod between appropriately profiled cylinders. Hitherto, however, it has not been possible to produce ribs on the already coldhardened surface of the rod, of sufficient height to provide positive anchoring of the rod in the concrete, and wherein there would be a continuous and gradual transition between the ribs and the unribbed portion of the rod.

An object of the invention is to provide a process for the manufacture of reinforcing rods wherein the ribs have a sufiicient height and blend smoothly with the unribbed surface of the rod.

According to the invention, this objective is attained by producing a steel rod of round cross-section by hot rolling, then reducing this cross-section by cold forming, e.g. drawing, then providing the rod at 2 to 4 locations uniformly distributed around its circumference with fiat indentations by cold-rolling in an axial direction, each of which indentation has a width .of to 30% of the rod diameter, whereafter the portions of the circumference lying between the flat indentations are provided with ribs United States Patent O 3,494,164 Patented Feb. 10, 1970 by cold-rolling in such a manner that there is a gradual transition from the flanks of the ribs with the. surface of the rod between the ribs and from the ends .of the ribs into the unribbed surface lying between two ribs in the circumferential direction.

The fiat indentations may also be produced by the cold forming methods by which the cross-section of the hot rolled rod is reduced. Generally, however, it is appropropriate to carry out these two steps of the process in succession. The production of the ribs is effected by means of as many rolls arranged around the rod as there are flat indentations therein. The circumference of these rolls is provided with many toothlike protuberances at distances corresponding to the distance desired between the ribs to be formed and the outer edges of which correspond to the shape of the notches which are to be formed on the rod between two ribs. According to the invention, the depth of the hollow formed between two adjacent projections at the circumference of the roll is a maximum in a central location along the length of the hollow, said depth being greater than the maximum height of the ribs of the steel rod which it forms. Preferentially, these hollows are such that at their greatest depth they lie on a cylindrical surface concentric with the rod axis but of a smaller diameter than the rod diameter, whereas their edges lie on a cylindrical surface concentric with the rod axis, which has a diameter greater than that of the rod, the width of these hollows in their center being approximately 20 to 25% of the rod diameter and becoming zero at the opposite ends of the hollows. The aforesaid two cylindrical surfaces intersect each other at the ends of the hollows, these points of intersection in the circumferential direction being separated by a distance of between 10 and 15% of the rod diameter.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a diagrammatic illustration of the drawing of a round rolled rod;

FIGURE 2 is a cross-sectional view on an enlarged scale .of a drawn round rod;

FIGURE 3 is a cross-section of a drawn rod which has been provided with fiat surfaces at three locations along its circumference;

FIGURE 4 is a perspective view of the rolls for producing the flat surfaces on the rod;

FIGURE 5 is a cross-sectional view of a rod provided with ribs according to the invention;

FIGURE 6 is a perspective view of the rolls for producing the ribs on the rod;

FIGURE 7 is a sectional view taken along line VII VII in FIG. 6;

FIGURE 8 is a diagrammatic view of the rod and a roll which forms the ribs;

FIGURE 9 is a perspective view of a rod according to the invention on an enlarged scale; and

FIGURE 10 is a sectional view taken along line XX in FIG. 8.

DETAILED DESCRIPTION For producing a concrete reinforcing rod according to the invention, the following operations are carried out.

A round rod 1 produced by hot rolling, which has a diameter d is drawn through a drawing nozzle 2, without having previously been heated to a temperature higher than the recrystallization point. Usually, drawing without any preheating of rod 1 suffices. By the drawing, the diameter d of the resulting rod 1' is reduced by about 10% compared to the diameter d Thereby, simultaneously, the tensile strength of the rod is increased. During cold drawing, the rod undergoes a calibration, i.e. an equalization of its cross-sectional size.

Moreover, by reducing the cross-sectional area of the rod of the order of 4 to 15%, its tensile strength is increased from 57,000 p.s.i. to about 71,000 p.s.i.

The rod 1 produced in this manner is then formed, as shown in FIGS. 3 and 4, with three flat surfaces 4a, 4b, 40, by means of the three rolls 3a, 3b, 30 which are arranged around the circumference of the rod at intervals of 120. The rolling is effected at a temperature which is lower than the recrystallization temperature of the rod, preferably without the application of any heat at all.

The rod 1" which now has the flat surfaces, is subsequently provided with the ribs 6a, 6b, 60 by means of the three rolls 5a, 5b, 50 which, again, are arranged at 120 intervals, as shown in FIGS. 6 and 7. The crosssection of the rod 1" produced in this manner is shown in FIG. 5 and a view in perspective is shown in FIG. 9.

In FIG. 8, the cross-section of rod 1" accordin to FIG. 3, is shown in dot-dash outline. Further, only part 5 of one of the rolls 5a, 5b, 5c is represented. The hollow 7 of this roll is limited on one side by the line 7, which corresponds to the surface of the rod 1" about to be produced and lies axially between the ribs, and on the other side by the line 7" which determines the depth of the hollow (see also FIG. From the point of view of roll portion 5, the line 7' protrudes beyond the dotdash line which circumscribes the cross-section 1". Thus, this edge of roll portion 5 displaces the material of the rod. This displacement of material occurs mainly into the hollow 7, which produces the rib 6. Consequently, the rib which is formed (see also FIG. 9), has a height h from the surface 8 of the rod (which corresponds to line 7') which is greater than the distance between the peripheral line 7' of the roll portion 5 and the periphery of the rod 1". However, the maximum height h of the ribs from the surface 8 is smaller than the maximum distance e between the lines 7' and 7", i.e. smaller than the depth of hollow 7. Thus, there remains a free space between the upper ridge of the ribs and the bottom of the hollows (see also FIG. 10). The hollow 7 has slanted sides 11, which blend into the surfaces 7' with rounded portions 10. The height and the Width of the hollow 7 decrease from the center of the hollow (where both are maximum) gradually towards the edges where their dimension becomes zero. Due to the presence of the flattened portions 4a, 4b, 4c of the cross-section of the rod 1", when the ribs are formed by means of the rolls 5a, 5b, 50, some amount of material is displaced into the area of the flattened portions, so that the ribs 6 which diminish in their height and Width towards their ends will gradually run out to zero in their transition into the non-ribbed portion of the rod surface.

What isclaimed is:

1. A process for producing a reinforcing rod for concrete, said process comprising forming a plurality of axially extending flat portions on the circumference of a cylindrical rod at equal angular intervals, the flat portions being formed with a width which is between 10 and 30% of the diameter of the rod, and cold working the rod to form in the regions between the flat portions a plurality of spaced ribs which protrude from the surface of the rod and are formed with lateral flanks smoothly blending with the surface of the rod between the ribs, and with ends smoothly blending into the flat portions.

2. A process as claimed in claim 1, wherein said cylindrical rod is formed by cold-working a hot-rolled rod to reduce the diameter of the latter and increase its tensile strength.

3. A process as claimed in claim 2, wherein said ribs are formed to extend at an angle with respect to the axis of the rod.

4. A process as claimed in claim 3, wherein said flat portions are formed by cold-rolling the rod in axial direction.

5. A process as claimed in claim 4, wherein the cold working of the rod to form the ribs is a cold-rolling operation.

6. A process as claimed in claim 2, wherein said coldworking of the cylindrical rod to reduce its diameter is a drawing operation. 1

7. A process as claimed in claim 1, wherein said ribs are formed by forcibly contacting the rod in each of the regions between the flat portions with a roll having a hollow corresponding to the shape of the ribs but with a depth greater than the height of the ribs to be formed.

8. A process as claimed in claim 7, wherein said hollows are formed with a maximum depth and width at the center of their length and gradually diminish to zero at their ends.

9. A process as claimed in claim 8, wherein the hollows are formed at their centers in the region of maximum depth with a width corresponding to about 20 to 25% of the diameter of the rod.

10. A process as claimed in claim 1, wherein said flat portions are between two and four in number.

11. A device for forming ribs in a reinforcing rod for concrete comprising a plurality of rolls arranged at equal angles to each other around the rod axis, the rolls having hollows each of gradually decreasing width which in the region of their greatest depth are located on a cylindrical surface having its axis parallel to the rod axis and with a diameter smaller than the diameter of the rod, the ends of the hollows which are located at the surface of the rolls being located on a cylindrical surface having its axis parallel to the rod axis and with a diameter greater than that of the rod, the hollows having a width at the center of their length which is about 20 to 25% of the diameter of the rod, the width of the hollows diminishing from the center to the opposite ends whereat the width of the hollows is zero, the aforesaid cylindrical surface at the bottom of each hollow intersecting said cylindrical surface at the ends of the hollows, and at said ends the circumferential distance between said ends corresponding to about 10 to 15% of the diameter of the rod.

References Cited UNITED STATES PATENTS 1,428,561 9/1922 Schuster 72-l91 2,347,904 5/ 1944 Greulich 72366 2,821,727 2/ 1958 Corckran 72--191 CHARLES W. LANHAM, Primary Examiner LOWELL A. LAIRSON, Assistant Examiner US. Cl. X.R. 72l94, 366 

